This research program is concerned with the elucidation of the genetic control of cellular differentiation in a relatively simple microbial model system, sporulation in Bacillus subtilis. A bacteriophage-host relationship will be used as a probe for investigation of basic regulation of cell development. Detailed analysis of phage gene expression in infected host cells during cell development and in infected mutants blocked in different stages of cell differentiation will be made by use of well defined DNA segments of the phage genome. Possible relationships between the alteration of host membrane components and abortive infection of phages during the early stages of sporulation will also be investigated. These studies are aimed at elucidating the nature of the basic control of cellular differentiation. BIBLIOGRAPHIC REFERENCES: Susceptibility of non-thymine containing DNA to four bacterial restriction endonucleases. J. Ito, F. Kawamura and J.J. Duffy. FEBS Letters 55: 278-281 (1975). Analysis of phi 29 and phi 15 genomes by bacterial restriction endonucleases, EcoR1 and HpaI. J. Ito, F. Kawamura and S. Yanofsky. Virology. March Issue (1976) (in press).